Research reveals association between red hair gene and rare birthmarks

11 May 2012

Research carried out at the UCL Institute of Child Health and Great Ormond
Street Hospital has identified that the
gene causing red hair - melanocortin-1-receptor (MC1R) - is more common in
children with Congenital Melanocytic Naevi (CMN), a rare form of birthmark.

CMN are rare brown or black birthmarks
which cover up to 80% of the skin surface area. They can vary in size
and number, and can occur anywhere on the body. The incidence of larger or
multiple lesions is approximately 1 in 20,000 new births per year.

In the
study published in the Journal of Investigative Dermatology, 166 people with
CMN had their hair and eye colour recorded, and had their blood checked for the
MC1R gene. Results were compared to a local control group of 60 unrelated
children and with 300 UK children without CMN from the Children of the 90s
study (ALSPAC) at the University of Bristol.

The changes
in the gene causing red hair (MC1R) were found to be more common in
children with CMN and in their families, than those without the
condition. In particular, children with CMN were much more likely to
carry two copies of those changes, one from each parent.

Researchers also identified that certain changes in the gene are associated
with children having much more severe skin changes, for example a larger CMN,
indicating that MC1R genotype influences the development of these birthmarks
when the child is in the womb.

This study shows an association between the gene that causes red hair and CMN. The gene seems to make CMN more likely to develop, particularly if the child has inherited a copy of the gene from each of their parents.

Dr Veronica Kinsler

Dr Veronica
Kinsler runs the paediatric pigmentary service at GOSH and has a weekly clinic
for CMN. She explains: "CMN is a very rare condition, and currently there
are no good medical treatments for it. In order to find treatments we
need to understand what caused the birthmarks to occur in the first place, and
therefore we are investigating the genetics of CMN.

"This study
shows an association between the gene that causes red hair and CMN. The
gene seems to make CMN more likely to develop, particularly if the child has
inherited a copy of the gene from each of their parents. Also some
variants of the gene are associated with the CMN being larger.

"If you
have red hair in your family, these findings should not worry you, as changes
in the red hair gene are common, but large CMN are very rare. So the
changes do not cause the CMN to happen, but just increase the risk."

CMN
birthmarks can be associated with moles also in the brain, and more rarely with
skin cancer (melanoma). Doctors at Great Ormond Street Hospital regularly
check patients for signs of any developments, for example by carrying out MRI
scans of the brain. But there is a need for improved treatments for such
complications relating to CMN.

Dr Veronica
Kinsler explains: "The genetic studies we are doing are also helping to
identify which children are at highest risk of these complications. In
particular, carrying the changes in MC1R which cause red hair is already known
to be associated with melanoma, so this may partly explain why children with
CMN have an increased risk of skin cancer. But again, I'd like to stress
that families with red hair should not worry as CMN is very rare."

An
unexpected finding in the study was that the same changes in the red hair gene
that were associated with larger birthmarks also seem to have a more
general effect on foetal growth - babies with those particular changes had a
significantly higher birth weight than those without. This was confirmed
in both the CMN group and in the control group from the Children of the 90s
study.

Dr Kinsler
says: "The effect on birthweight was a complete surprise. We looked
for it when we noticed that certain changes in the gene were associated with
the CMN being larger, and wondered if they affected growth more
generally. However, it is important to stress that this is a relatively
small study for looking at birthweight, and we are now checking this finding in
a much larger group of people without CMN."

Doctors at Great Ormond Street Hospital estimate
there are only around 3,000 individuals with severe CMN at the moment in the
UK, with lots more who are mildly affected.

The
research was funded by the Wellcome Trust and Caring Matters Now charity.